It was in the area of agriculture that the Middle Ages surpassed antiquity in the use of the horse. This was especially true in the area of agriculture. The ancient world preferred to use oxen for ploughing: and writers from Hesiod through Columella stressed the importance of the ox is this area. However, Pliny does mention the use of the donkey for ploughing1. The type of plough generally used in Italy was the scratch plough or ard. It did not dig deeply into the soil. This type of plough prevailed throughout the Italian Peninsula and into Egypt and portions of the Eastern Roman Empire. There are some difficulties in tracing the evolution of the plough from the scratch to the Medieval heavy plough with a moldboard, which allowed the plough to dig deeply into the heavier soil of what is now western Europe and lay the earth over in furrows.
Pliny mentions a heavy plough (plaumoratum) which was used in Raetian Gaul. He describes it as similar to a heavy plough whose ploughing blade was broader and d sharper than a heavy plough and was and shaped like a spade. The plaumoratum also added a pair of small wheels2. "Later Romano-British ploughs were heavier, enabling deeper soil penetration, and from the late third and fourth centuries AD they included a coulter, which ran through the soil in front of the share."3 Since archaeological evidence also dates the existence of some sort of wheeled plough in the 5th century4, I think the inescapable conclusion is that the Romans possessed some sort of heavy plough which was used in the areas of the Roman Empire where the soil was not suitable for a scratch plough5.
The evidence from numerous Latin writers on agriculture, Pliny, Virgil, Columella, Varro to name but a few indicate that the ox was the animal used for ploughing. The use of the ox remained popular and was the preferred animal for ploughing in some areas. Walter of Henley in his treatise on estate management, preferred the ox to the horse for ploughing. Also in many areas of England, specifically, north and west6 oxen were more frequently used than horses. In fact oxen remained the preferred farm animal in parts of Italy and the Iberian Peninsula well into the 19th century. Nevertheless for a large portion of Western Europe the horse became the dominant animal used for ploughing in the Middle Ages and beyond until he was displaced by the tractor.
With the preference for oxen as engine of ploughing there was no real need to construct a harness system which would allow the horse to pull a plough. The major problem with using either the dorsal yoke or the neck yoke to harness an equid to a plough is really the point of attachment. In wagons and carts the point of attachment was reasonably far off the ground, whereas for ploughs it is almost at ground level. Also wagons and cart had either shafts, or a draught pole which formed part of the attachment of the equid to the vehicle. It was the need to find some satisfactory method for lowering the attachment point that led to the spread of the horse collar rather than its use as an instrument providing superior traction in hauling.
- Pliny, 8.167
- Pliny, 18.171-173
- Fossier, p. 280
- Brunner, pp. 25-27
- For evidence for heavy Roman ploughs see also Percival pp. 114-117; Salway, pp 622-3; Dark, pp 101-103
- Langdon, Brancards et Transport, p. 133